In a few years, nuclear fusion could possibly be used to generate large quantities of electricity in a climate-neutral and safe manner. However, there is still a long way to go before mass production due to the continuing major technical hurdles.
(Photo: dpa)
New York, Dusseldorf US scientists have made a long-awaited breakthrough in nuclear fusion. For the first time, the fusion of atomic nuclei produced more energy than was consumed, as US Energy Secretary Jennifer Granholm announced in Washington on Tuesday. “Put simply, this is one of the most impressive scientific achievements of the 21st century.”
To do this, researchers at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California generate fusion energy using what is known as “thermonuclear inertial fusion”. In practice, the scientists fire 200 lasers into a cavity. A globule of heavy hydrogen (deuterium) in this cavity is compressed and heated by the radiation, triggering nuclear fusion reactions. These in turn produce high-energy neutrons and alpha particles.
The energy of the neutrons and alpha particles then actually creates heat in the walls, which can be converted into electricity. What the NIF has successfully demonstrated currently takes a whole day. A power plant would have to manage the process more than ten times a second.
Nuclear fusion: important questions remain unanswered
The news is a minor sensation for fusion technology. It remains to be seen whether the overall balance will remain positive in the end, says Klaus Hesch, spokesman for the fusion program at the Karlsruhe Institute of Technology, putting the brakes on the euphoria. It is still unclear how much electrical power is required for the other systems in the reactor and what is really left over in the end.
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Also, the experiment’s ratio would need to be about 100 times larger to create a process that produces significant amounts of electricity. “That’s probably too inefficient for a power plant,” Sibylle Günter, Scientific Director of the Max Planck Institute for Plasma Physics, told the Handelsblatt. These and many other technological questions still have to be clarified before one can even think about building a power plant.
Since the 1930s, mankind has been dreaming of successful nuclear fusion, which in principle would enable artificial energy from the sun to be used on earth. Inside the sun, hydrogen nuclei fuse to form helium nuclei, releasing a great deal of energy. So far, however, all attempts to mimic this fusion on Earth have failed.
The biggest problem: positively charged atomic nuclei usually do not combine. The so-called “Coulomb barrier” can only be overcome under very special circumstances – a high use of energy and extremely high temperatures are a prerequisite.
In Cadarache, southern France, scientists from two dozen countries have been trying for a long time to get the Iter reactor process going. However, not with lasers, but through the use of huge magnets. They produce nuclear fusion in extremely hot plasma clouds. According to the current status, a first experimental reactor can be expected in 2035 at the earliest, with commercial use much later. A stable, reproducible process has not yet been achieved, and a positive energy balance is a long way off.
Several start-ups and research institutes therefore believe that they have found the solution in high-performance lasers and other fuels, such as those used by the NIF. Among them are German companies such as Marvel Fusion from Munich or Focused Energy from Darmstadt.
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After ten years, the laser-based processes are actually showing their first successes. It could again be a few years before the next notable advance is announced. Because the current process is too inefficient to use it in a real power plant and to generate significant amounts of energy.
According to Günter, however, the viable alternative is much more susceptible to instabilities. “It will certainly take ten years to find a suitable scenario.” If it works at all. “There is still a lot of basic research to be done,” says the nuclear physicist.
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